diff --git a/lib/storage/merge.go b/lib/storage/merge.go
index 0fc16d434..433b2fc4e 100644
--- a/lib/storage/merge.go
+++ b/lib/storage/merge.go
@@ -3,6 +3,7 @@ package storage
 import (
 	"fmt"
 	"sync"
+	"sync/atomic"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/decimal"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
@@ -53,12 +54,12 @@ func mergeBlockStreamsInternal(ph *partHeader, bsw *blockStreamWriter, bsm *bloc
 		}
 		if dmis.Has(bsm.Block.bh.TSID.MetricID) {
 			// Skip blocks for deleted metrics.
-			*rowsDeleted += uint64(bsm.Block.bh.RowsCount)
+			atomic.AddUint64(rowsDeleted, uint64(bsm.Block.bh.RowsCount))
 			continue
 		}
 		if bsm.Block.bh.MaxTimestamp < retentionDeadline {
 			// Skip blocks out of the given retention.
-			*rowsDeleted += uint64(bsm.Block.bh.RowsCount)
+			atomic.AddUint64(rowsDeleted, uint64(bsm.Block.bh.RowsCount))
 			continue
 		}
 		if pendingBlockIsEmpty {
@@ -181,7 +182,7 @@ func skipSamplesOutsideRetention(b *Block, retentionDeadline int64, rowsDeleted
 	for nextIdx < len(timestamps) && timestamps[nextIdx] < retentionDeadline {
 		nextIdx++
 	}
-	*rowsDeleted += uint64(nextIdx - b.nextIdx)
+	atomic.AddUint64(rowsDeleted, uint64(nextIdx - b.nextIdx))
 	b.nextIdx = nextIdx
 }